Scattered radiation smoke detector

ABSTRACT

In a scattered radiation smoke detector (D) the energy supply from the evaluation unit (A) and the signal returned thereto take place exclusively optically by means of radiation conducting elements (L 1 , L 2 ) and all electrical components are situated in the evaluation unit (A) remote from the smoke detector (D). An approximately parallel transmitting or reception zone of small diameter is generated by collimating devices (4, 6) disposed at the ends (3, 8) of the optical conductors and thereby the interference radiation level in the smoke detector is reduced and the sensitivity increased. Since the smoke detector (D) comprises no metallic components, it is insensitive to temperature and corrosion and is especially well suited for application in environments subject to the danger of explosion and electrical interference.

CROSS REFERENCE TO RELATED CASE

This application is related to the commonly assigned, copending U.S.application Ser. No. 06/606,827, filed Apr. 16, 1984, entitled"PHOTOELECTRIC SMOKE DETECTOR AND IT'S APPLICATION", and listing as theinventor HANNES GUTTINGER et al.

The present invention broadly relates to a smoke detection systems and,more specifically, pertains to a new and improved scattered radiationsmoke detector.

Generally speaking, the smoke detection system of the present inventionemploys a scattered radiation smoke detector for generating an alarmsignal in response to detection of smoke and comprises an electronicevaluation circuit. The electronic evaluation circuit comprises meansfor generating the alarm signal in response to electromagnetic radiationscattered by smoke and also comprises means for emitting electromagneticradiation. At least one radiation conducting element conducts thescattered radiation smoke detector to the evaluation circuit. Theelectromagnetic radiation emitted by the electronic evaluation circuitis radiated into a measuring volume. At least one radiation conductingelement is provided through which said electromagnetic radiation isradiated into said measuring volume. At least one radiation conductingelement is provided by which the electromagnetic radiation scatteredfrom smoke particles in the measuring volume is received and transmittedback to the electronic evaluation circuit.

In other words, the smoke detection system of the present invention isof the type comprising a scattered radiation smoke detector containing ameasuring volume, an evaluation circuit having means for emittingelectromagnetic radiation as well as means for generating an alarmsignal upon detecting presence of smoke in the measuring volume and atleast one optical conductor pair connecting the evaluation circuit tothe scattered radiation smoke detector.

In a further embodiment, the present invention relates to a scatteredradiation smoke detector comprising an electronic evaluation circuit anda plurality of electromagnetic radiation conducting elements forconnecting the electronic evaluation circuit to the smoke detector. Theelectronic evaluation circuit comprises means for emittingelectromagnetic radiation. The scattered radiation smoke detector alsocomprises a measuring volume. At least one first electromagneticradiation conductor of the plurality of electromagnetic radiationconductors serves for radiating the electromagnetic radiation emitted bythe means into the measuring volume and at least one secondelectromagnetic radiation conducting element of the plurality ofelectromagnetic radiation conducting elements serves for receiving andconducting back to the electronic evaluation circuit electromagneticradiation scattered by smoke particles in the measuring volume.

The invention relates to a scattered radiation smoke detector which canbe connected to an evaluation unit by means of radiation conductingelements and in which the electromagnetic radiation transmitted from theevaluation unit is beamed into a measuring volume through at least oneradiation conductive element and electromagnetic radiation scattered bysmoke particles in the measuring volume are received by at least oneradiation conducting element and transmitted back to the evaluationunit.

In heretofore known scattered radiation smoke detectors, such as areknown from U.S. Pat. No. 4,181,439 or Patent Cooperation TreatyApplication WO No. 80/01326, electromagnetic radiation, which is to beunderstood to include visible light, infrared radiation or ultravioletradiation, is radiated into an extensive measuring volume by a lightemitting diode (LED) disposed in the interior of the smoke detector andradiation scattered by smoke particles in the direction of a solar cellalso disposed in the interior of the smoke detector is received by thesolar cell.

For voltage supply and signal transmission the smoke detector isconnected to an evaluation unit or central signal station by means ofelectrically conductive metallic signal conductors.

Due to the metallic conductors and to the electrical circuits presentwithin the smoke detector, at least in the diode control circuit and inthe receiver circuit, such smoke detectors cannot be used in regionssubject to the danger of explosion without complicated and expensiveprotection and safety measures. A further disadvantage is theundesirable temperature characteristics of the electrical componentswhich require complicated compensation measures. Under certainenvironmental conditions there is also the risk of corrosion of metalparts. Certain components are also sensitive to water and moisture. Thisrequires a complicated design and complicated manufacturing processessuch as protecting the components with a potting material etc.

These disadvantages can partly be overcome, as for instance is describedin Belgian Pat. No. 881,812 or in German patent application No.3,037,636, by connecting the smoke detector with the evaluation unit bymeans of radiation conducting elements, also known as optical conductorsor fiber optics, and disposing the radiation source as well as theradiation receiver in the evaluation unit. The radiation is transmittedfrom the evaluation unit to the smoke detector by an optical conductor,is radiated into the measuring volume from the end or exit of thisoptical conductor in the detector, the scattered radiation from themeasuring volume is received by the input of another optical conductorand transmitted by this optical conductor back to the evaluation unit.There are therefore in the actual smoke detector no metallic leads orelectrical components, so that explosion safety, temperatureinsensitivity, moisture insensitivity and corrosion insensitivity areobtained.

A disadvantage of such smoke detectors is the relatively broad radiatingcharacter of the emission of the optical conductor, that is itsrelatively wide aperture angle, as well as the equally broad receptioncharacteristics of the optical conductor receiving the scatteredradiation. This has the result that in such smoke detectors onlyscattered radiation having a relatively wide angle of scattering, i.e. arelatively wide angle between the radiation beamed in and the radiationreceived, can be evaluated since at smaller angles of scattering asubstantial component of the received radiation consists of directradiation. In particular, the extreme forward scattering at scatteringangles close to 0° that are particularly useful for detecting smokecannot be detected by such smoke detectors. The broad radiatingcharacteristics have furthermore the effect that a large part of theinterior wall of the detector is irradiated by direct radiation andpartially reflects it, particularly due to dust precipitated on the wallwhich is hardly to be avoided in the course of operation. This leads toan illumination of the measuring volume and to a level of interferenceenergy which masks any radiation weakly scattered by smoke and rendersit indetectable or can initiate a false alarm. Therefore, theilluminating power of the radiation source and with it the powerrequirements of the smoke detector could not be kept at a desirably lowlevel and complicated and expensive measures were required to avoid dustprecipitation and radiation reflection from the interior walls of thedetector.

A certain improvement was achieved by providing optical means forconcentrating the radiation on a focal line or to a focal point, as is,for instance, described by the publications mentioned above. Since theradiation diverges again beyond the focal line or the focal point, toogreat a portion of the interior wall is still struck by direct radiationand the level of interference radiation is still undesirably high. If ananalogous focussing optical means is also provided ahead of thereceiver, a precise adjustment of the impinging radiation at the focalpoint is required, which complicates manufacturing and increases costs.The adjustment can also deteriorate in the course of time due to theeffect of temperature or vibrations so that sensitivity is reduced orlost.

Finally, it is difficult, due to mutual encumbrance, to provide two ormore sources of radiation in a detector, which would otherwise beadvantageous for distinguishing various types of particles andpermitting an intelligent evaluation of signals.

SUMMARY OF THE INVENTION

Therefore, with the foregoing in mind, it is a primary object of thepresent invention to provide a new and improved construction of ascattered radiation smoke detector which does not exhibit theaforementioned drawbacks and shortcomings of the prior artconstructions.

Another and more specific object of the present invention is toeliminate the disadvantages of the prior art devices mentioned above andespecially to provide a scattered radiation smoke detector of thepreviously mentioned type which is not only explosion-proof andinsensitive to temperature, moisture and corrosion, but also has anincreased sensitivity, a low susceptibility to interference and falsealarm, as well as improved reliability even when subject to longerdurations of operation and to dust accumulation in difficultenvironmental conditions.

These objects are realized according to the invention by providing atthe radiation beam exit point or at the radiation beam entry point ofthe radiation conducting elements collimating devices for generating anat least approximately non-divergent radiating or receiving zone (S, E)of small cross-section and arranging and orienting the collimatingdevices and the radiation conducting elements such that the radiatingand receiving zones intersect.

In other words, the scattered radiation smoke detector of the presentinvention is manifested by the features that the at least two radiationconducting elements each have a radiation exit and a radiation entry andat least two collimating devices are provided each at a associated oneof the radiation exits and the radiation entries for generating anappropriate one of an at least approximately non-divergent transmittingzone of small cross-section and an at least approximately non-divergentreceiving zone of small cross-section. The radiation conducting elementsas well as the collimating devices are arranged and oriented such thatthe transmitting and receiving zones thereof intersect. The at least tworadiation conducting elements define a forward direction in which theelectromagnetic radiation is radiated into the measuring volume. Thecollimating devices are structured and oriented such that thetransmitting and receiving zones define at least approximately parallelbeams which intersect at acute angles such that each receivingcollimating device of the collimating devices receives radiationscattered at an acute angle in the forward direction.

In other words, the smoke detection system of the present invention ismanifested by the features that the scattered radiation smoke detectorcomprises at least one first optical collimator for directingelectromagnetic radiation into The measuring volume in a predeterminatedirection. The at least one optical conductor pair comprises at leastone optical transmission conductor for conducting the electromagneticradiation from the means for emitting electromagnetic radiation to theat least one first optical collimator. The scattered radiation smokedetector comprises at least one second optical collimator for receivingelectromagnetic radiation forward-scattered from smoke within themeasuring volume. The at least one optical conductor pair comprises atleast one optical reception conductor for conducting the receivedforward-scattered electromagnetic radiation back to the evaluationcircuit. The evaluation circuit comprises means for sensing andevaluating the electromagnetic radiation conducted back for determininga possible presence of smoke in the measuring volume. The at least onefirst optical conductor defines a radiation zone extending in thepredetermined direction and substantially confined to a diameter of lessthan 3 mm (substantially non-divergent). The at least one second opticalconductor defines a forward-scattering reception zone extending at anangle of less than 90° to said predetermined direction and substantiallyconfined to a diameter less than 3 mm (substantially non-divergent). Theforward-scattering reception zone intersects the radiation zone withinthe measuring volume.

A further embodiment of the scattered radiation smoke detector of thepresent invention is manifested by the features that the at least onefirst electromagnetic radiation conductor has an electromagneticradiation exit end. The at least one second electromagnetic radiationconductor has an electromagnetic radiation entry end. A respectiveoptical arrangement is provided at each of the electromagnetic radiationexit end and the electromagnetic radiation entry end. Each opticalarrangement comprises a radiation emission collimating device and aradiation reception collimating device. Each optical arrangement definesan at least approximately non-divergent radiation zone of smallcross-section and an at least approximately non-divergent reception zoneof small cross-section. The at least approximately non-divergentradiation zone of small cross-section and the at least approximatelynon-divergent reception zone of small cross-section of both opticalarrangements mutually intersect in the measuring volume for generatingthe at least approximately non-detergent radiation zone of smallcross-section and the at least approximately non-divergent receptionzone of small cross-section.

In other words, this alternate embodiment of the scattered radiationsmoke detector is manifested by the features that the scatteredradiation smoke detector comprises at least two first opticalcollimators for directing electromagnetic radiation into the measuringvolume in a predetermined direction. The at least two optical conductorpairs comprises at least two optical transmission conductors forconducting the electromagnetic radiation from the means for emittingelectromagnetic radiation to each of the at least two first opticalcollimators. The scattered radiation smoke detector comprise at leasttwo second optical collimators for receiving electromagnetic radiationforward-scattered from smoke within the measuring volume. The at leasttwo optical conductor pairs comprise at least two optical receptionconductors for conducting the received forward-scattered electromagneticradiation back to the evaluation circuit. The evaluation circuitcomprise means for sensing and evaluating the electromagnetic radiationconducted back by each of the at least two optical reception conductorsfor determining a possible presence of smoke in the measuring volume.The at least two first optical collimators define at least two radiationzones extending in the predetermined direction and substantiallyconfined to diameters of less than 3 mm (substantially non-divergent).The at least two second optical collimators define at least twoforward-scattering reception zones each extending at an angle of lessthan 90° to the predetermined direction and substantially confined todiameters of less than 3 mm substantially non-divergent. The at leasttwo forward-scattering reception zones intersecting the at least tworadiation zones within the measuring volume.

A further embodiment of the present invention is manifested by thefeatures that the at least one first optical collimator defines aradiation zone having substantially the form of a conical surface ofrevolution generated about an axis of revolution extending in thepredetermined direction and substantially confined to a small thickness;the at least one second optical collimator defining a forward-scatteringreception zone having substantially the form of a conoid or conicalsurface of revolution generated about an axis of revolution extending inthe predetermined direction and substantially confined to a smallthickness. The radiation zone intersects the forward-scatteringreception zone in a substantially circular ring of small diameter withinthe measuring volume.

The combination of radiation conducting elements with suitablecollimating devices permits close limitation of the radiating andreceiving zones to parallel beams having diameters of, for example, lessthan 3 mm in a simple manner without recourse to complicated means suchas lasers. In this way, an arrangement can be designed which receivesexclusively extreme forward scattered radiation yet practically nodirect radiation and is insensitive to slight alterations of adjustment.Since only a tiny spot of the interior wall of the detector is directlyilluminated, interfering scattered radiation from this point can bepractically entirely eliminated by simple measures, such as small buthighly effective radiation traps or apertures. An analogous radiationtrap can also be provided in the receiving zone. Neither is it difficultto provide a plurality of radiating and receiving zones.

The scattered radiation smoke detector of the invention, as well aspractical and advantageous further embodiments thereof, will now bedescribed in relation to the exemplary embodiments shown in thedrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood and objects other than those setforth above will become apparent when consideration is given to thefollowing detailed description thereof. Such description makes referenceto the annexed drawings wherein throughout the various figures of thedrawings there have been generally used the same reference characters todenote the same or analogous components and wherein:

FIG. 1 is a schematic representation of the arrangement of a smokedetector,

FIG. 2 is a cross-section through a scattered radiation smoke detector;

FIG. 3 is a schematic representation of a smoke detector for theevaluation of a plurality of scattering angles;

FIG. 4 is a schematic representation of a smoke detector for evaluatinga plurality of wavelengths;

FIG. 5 is a schematic representation of a smoke detector for monitoringradiation;

FIG. 6 is a schematic representation of a smoke detector having aplurality of scattering spaces;

FIG. 7 is a schematic cross-section of a smoke detector having acone-shaped radiation zone.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS

Describing now the drawings, it is to be understood that to simplify theshowing thereof only enough of the structure of the scattered radiationsmoke detector has been illustrated therein as is needed to enable oneskilled in the art to readily understand the underlying principles andconcepts of this invention. Turning specifically to FIG. 1 of thedrawings, the smoke detection system illustrated therein by way ofexample and not limitation will be seen to comprise, a scatteredradiation smoke detector D connected to an evaluation unit or electronicevaluation circuit A by means of radiation conductive elements oroptical conductors L₁ and L₂. While the smoke detector D is disposed ata measuring location of a space to be monitored, the evaluation unit Acan be remotely located, if necessary at a distance of more than 100 m.The construction of each optical conductor L₁, L₂ is advantageouslyadapted to the radiation employed and can be of the multimode ormonomode type. The optical conductors L₁ and L₂ can consist of a singlefiber or of a bundle composed of a plurality of radiation conductingfibers. According to the construction of the smoke detector D, two ormore optical conductors L₁, L₂ may be required for the connection to theevaluation unit. Furthermore, a plurality of smoke detectors D can beconnected to the evaluation unit A in parallel through the same opticalconductor L₁, L₂ by means of known gating devices or by means ofindividual optical conductors on the same input.

In the arrangement shown, a driver circuit 1 provided in the evaluationunit or circuit A regulates a radiation emitting diode (LED) 2 in pulsedoperation at 0.1-10 kHz. Its radiation, which according to the type ofLED, may be visible, infrared or ultraviolet, is introduced into theoptical conductor L₁ and transmitted through it to the smoke detector D.A collimating device 4 is disposed at the radiation exit 3 of thisoptical conductor L₁. The collimating device is a special optical device4 which collimates the radiation emitted from the end of the opticalconductor L₁ into an at least approximately parallel radiation beam S. Afurther collimating device 6, shielded from direct radiation by adiaphragm 5, is disposed outside of this radiation beam S and has itsreception zone E oriented such that it receives radiation scattered fromsmoke particles out of a scattering volume 7 and conducts it to aradiation entry 8 of the second optical conductor L₂ which, in turn,conducts the received scattered radiation to a solar or photo detectioncell 9 in the evaluation unit or circuit A. This solar orphoto-detection cell converts the received radiation, i.e. the opticalsignal, into an electrical signal which is amplified by an inputamplifier 10. The output signal of the input amplifier 10 is transmittedto a signal processing circuit 11 which also receives a reference signalfrom the driver circuit 1 through an electrical conductor 12 and in turntransmits a signal to a subsequent alarm circuit 13 only when thetransmitted and received radiation coincide. Alarm circuit 13 activatesan alarm device 14 when the scattered radiation signal exceeds aprescribed threshold.

In an evaluation unit realized in practice, the following circuitcomponents were employed:

Driver 1: Oscillator with 555-Timer (Signetics) and 7473 Flip-Flop forgenerating a square wave voltage at approximately 270 Hz.

LED 2: 2 SE 3352 (Honeywell)

Optical Conductor: QSF 200 A (Quartz et Silice)

Collimator 3, 8: SELFOC SLW 1.8/0.23 P (Nippon Sheet Glass)

Solar or photo detection Cell 9: PIN BPX 65 Siemens)

Input amplifier 10: ICL 7621 (Intersil)

The signal processing circuit 11 can, for instance, be constructed as acoincidence circuit for smoke detectors as known from European Pat. Nos.EP 11,205 or EP 14,779 or can comprise a phase sensitive amplifier(Lock-in amplifier) such as is available from Princeton Applied ResearchCorporation.

FIG. 2 shows the construction of a smoke detector D carried out inpractice according to the invention in section. A plastic base plate 20carries an air permeable housing 21 enclosing a measuring chamber M anda carrier element 22 in the interior, also made of a suitable plastic.An optical conductor connection or plug connection C of known type isprovided in the base plate 20 and serves to connect the opticalconductors L₁, L₂ coming from the evaluation unit A to the opticalconductor connections 23 and 28 situated in the interior of thedetector. The two collimating devices 24 and 26 are mounted in recessesin a carrier element 22 and cooperate with the ends of the opticalconductor connectors 23 and 28 such that a radiating zone S or receivingzone E with very small aperture angle, i.e. nearly parallel radiation,and a small diameter, i.e. not more than 1 to 3 mm, is produced. Aplurality of shields 25 are installed on the central portion of thecarrier element 22 for shielding the direct residual radiation from thecollimator 26. The optical arrangement corresponds to the diagram ofFIG. 1. In order to avoid interference by light penetrating into themeasuring chamber M through the housing 21 or by radiation reflectedfrom the interior walls of the housing, the optical arrangement in theinterior of the housing 21 is enclosed by an air-permeable but radiationabsorbing labyrinthine element 27. This can, for instance, compriseintermeshing fins or be provided with radiation absorbent ribs on itssurfaces in order to eliminate the very last interference radiation, forinstance that from the edges of the shields 25. A radiation trap 30 ofsmall extent but of particularly good absorption characteristics can beprovided to collect the direct radiation emitted from the collimationdevice 24 and so can an analogous trap 31 at the end of the receivingzone E. Due to the good collimation and the extremely small diameter ofthe radiation zone S, which were not attainable in heretofore knownscattered radiation smoke detectors, the heretofore necessarycomplicated measures for eliminating interference radiation can in largemeasure be reduced or omitted in the design described or, on the otherhand, the sensitivity of the smoke detector D can be increased and itssusceptibility to false alarms reduced. For the same reasons, theoptical arrangement can be designed with a smaller scattering angle thanheretofore, so that the forward scattering, which is particularlysuitable for detecting smoke, can be evaluated, which heretofore wasonly possible by accepting a higher susceptibility to false alarm andreduced sensitivity. Forward scattering angles under 15° can be attainedwithout complicated shield systems and with suitable shields evenscattering angles down to 5°. Further advantages result from the factthat the smoke detector D can be constructed entirely of non-metallicmaterials, that is, it is fully explosion-proof, not subject toelectromagnetic interference, hardly susceptible to corrosion, alsosuited for high voltage applications and is furthermore extremelytemperature resistant, at least in the range between -50° C. and +150°C. or even considerably higher temperatures if the plastics are replacedby ceramics.

FIG. 3 shows the diagram of a smoke detector D which, in addition to thecomponents already represented in FIG. 1, comprises a furthercollimating device 15 which is capable of receiving scattered radiationat a greater scattering angle than the first collimating device 6 andwhich is connected to the evaluation unit A by a third optical conductorL₃. This permits the evaluation of the ratio of scattering at a lowscattering angle to scattering at a high scattering angle, which isdifferent for different types of smoke. With a suitable evaluationcircuit A it can therefore be determined what type of smoke is actuallypresent. The larger scattering angle can also be chosen greater than 90°so that one collimator receives the forward scattered radiation and theother the backward scattered radiation. A strongly absorbing, i.e.black, smoke can thus be differentiated from a strongly reflecting, i.e.white, smoke.

In the arrangement shown in FIG. 4, two different LED's 2¹ and 2² areprovided in the evaluation unit A to transmit radiation at two differentwavelengths. Both radiation components are gated into the same opticalconductor L₁ by means of a gating element 16 and transmitted to thecollimating device 4. By separate evaluation of the scattered radiationat the two wavelengths, information can be gained about the nature ofthe scattering medium, particularly about the particle size.

Smoke detector D according to FIG. 5 comprises a further radiationreceiving collimator 17 disposed in the extension of the radiationdirection of the collimator 4, and which receives direct radiation andtransmits it through a further optical conductor L₄ to the evaluationunit A. In this manner the functioning of the LED can be monitored, thatis should the radiation fail, a signal will be given or should theintensity of radiation slowly vary, the LED can be regulated.

In the smoke detector D represented in FIG. 6 a second system or opticalarrangement comprising the collimators 4² and 6², the optical conductorsL₅ and L₆ and the shield 5² is disposed in close proximity to a firstsuch system or optical arrangement comprising the collimators 4¹ and 6¹,the optical conductors L₁ and L₂ and the shield 5¹, to which the secondsystem is analogous. It can be determined by means of a coincidencecircuit in the evaluation unit A if scattered radiation is present inboth systems simultaneously in order to avoid false alarms.

The transmitting region S and the receiving region E can be embodiedother than as parallel beams of small diameter. FIG. 7 shows anexemplary embodiment of such a smoke detector D. This, like the smokedetector D according to the example of FIG. 1, is connected to anevaluation unit A by two optical conductors L₁, L₂ and at each of theentries and exits of the optical conductors 3 and 8 collimating devices4 and 6 are provided. In contrast to the previously describedembodiments, these collimating devices 4 and 6 are provided withaspherical surfaces, so that their transmitting or receiving zone hasthe configuration of a conical shell of small thickness. The radiationintensity or the reception sensitivity is substantially confined to theconical shell and is relatively low outside the shell as well as withinthe cone in proximity to the axis. The collimating optics are sostructured that the aperture angle of radiation in a generatrix of theconical shell is very small, i.e. the thickness of the transmitting orreceiving zone varies little along a generatrix. The transmitting andreceiving zones intersect in the example shown in a zone 7 having theconfiguration of a circuit ring or torus of small diameter. In this waysimilar advantages are obtained as in previously described embodimentshaving parallel transmitting or receiving zones as long as thedivergence of the transmitting and receiving zones, i.e. the variationin thickness of the transmitting and receiving zones, can be kept smallin the transmitting or receiving directions. In the embodiment accordingto FIG. 7, radiation traps 29 are provided for the absorption of directradiation and for avoiding the reception of background radiation. Theyare advantageously constructed as circular rings and annularly surroundthe collimating devices 4 and 6.

While there are shown and described present preferred embodiments of theinvention, it is to be distinctly understood that the invention is notlimited thereto, but may be otherwise variously embodied and practicedwithin the scope of the following claims. Accordingly,

What we claim is:
 1. A scattered radiation smoke detector for generatingan alarm signal in response to detection of smoke, comprising:anevaluation circuit comprising means for generating an alarm signal inresponse to electromagnetic radiation scattered by smoke and comprisingmeans for emitting electromagnetic radiation; at least two radiationconducting elements for connecting the scattered radiation smokedetector to the evaluation circuit; a measuring volume into which saidelectromagnetic radiation emitted by said evaluation circuit isradiated; at least one radiation conducting element through which saidelectromagnetic radiation is radiated into said measuring volume; atleast one radiation conducting element by which electromagneticradiation scattered from smoke particles in said measuring volume isreceived and transmitted back to said evaluation circuit; said at leastone radiation conducting element through which said electromagneticradiation is radiated into said measuring volume having a radiation exitand said at least one radiation conducting element for receiving saidscattered electromagnetic radiation having a radiation entry; at leasttwo collimating devices provided each at an associated one of saidradiation exit and said radiation entry for generating an associated oneof an at least approximately non-divergent transmitting zone of smallcross-section and an at least approximately non-divergent receiving zoneof small cross-section; said radiation conducting elements as well assaid collimating devices being arranged and oriented such that saidtransmitting and receiving zones thereof intersect; said at least oneradiation conducting element through which said electromagneticradiation is radiated into said measuring volume defining a forwarddirection in which said electromagnetic radiation is radiated into saidmeasuring volume; and said at least two collimating devices beingstructured and oriented such that said transmitting and receiving zonesdefine at least approximately parallel beams which intersect at an acuteangle such that one of said at least two collimating device receivesradiation scattered at an acute angle in said forward direction.
 2. Thesmoke detector as defined in claim 1, wherein:said acute angle isbetween 5° and 15°.
 3. The smoke detector as defined in claim 1,wherein:said transmitting zone has a diameter not greater than 3 mm. 4.The smoke detector as defined in claim 1, wherein:said receiving zonehas a diameter not greater than 3 mm.
 5. The smoke detector as definedin claim 1, further including:at least one shield arranged between saidat least two collimating devices; said at least two collimating devicescomprising said one collimating device defining at least one firstcollimating device for receiving radiation and at least one secondcollimating device for emitting radiation; and said at least one shieldshielding from direct radiation emitted by said at least secondcollimating device from said at least one first radiation receivingcollimating device.
 6. The smoke detector as defined in claim 5, furtherincluding:a further collimating device arranged and oriented such thatsaid further collimating device receives scattered radiation at agreater angle of scattering than said at least one first collimatingdevice.
 7. The smoke detector as defined in claim 6, wherein:saidscattering angle is at least 90°.
 8. The smoke detector as defined inclaim 1, wherein:said electromagnetic radiation comprises at least twodifferent ranges of wavelength.
 9. The smoke detector as defined inclaim 8, further including:a further collimating device arranged in adirect radiation zone.
 10. The smoke detector as defined in claim 1,further including:two optical arrangements; each optical arrangement ofsaid two optical arrangements comprising one of said at least twocollimating devices defining a radiation transmitting collimating devicehaving a transmitting zone and a a further one of said at least twocollimating devices defining radiation receiving collimating devicehaving a receiving zone; and said transmitting and receiving zones ofsaid two optical arrangements intersecting in adjacent measuringvolumes.
 11. The smoke detector as defined in claim 1, wherein:theemitted electromagnetic radiation has the form of pulses.
 12. The smokedetector as defined in claim 12, wherein:the smoke detector is capableof being connected to said evaluation circuit; said evaluation circuitcomprising a signal-processing circuit for comparing transmittedradiation to received radiation.
 13. The smoke detector as defined inclaim 12, wherein:said signal-processing circuit comprises a phasesensitive amplifier.
 14. The smoke detector as defined in claim 13,wherein:said phase sensitive amplifier comprises a lock-in amplifier.15. The smoke detector as defined in claim 1, wherein:said radiationzone is terminated by a radiation trap.
 16. The smoke detector asdefined in claim 15, wherein:said receiving zone is terminated by aradiation trap.
 17. The smoke detector as defined in claim 1,wherein:said at least two collimating devices are structured such thatsaid transmitting and receiving zones have the form of substantiallycone-shaped shells of small thickness which intersect in an annularmeasuring volume.
 18. A smoke detection system, comprising:a scatteredradiation smoke detector containing a measuring volume; an evaluationcircuit having means for emitting electromagnetic radiation and meansfor generating an alarm signal upon detecting a presence of smoke insaid measuring volume; at least one optical conductor pair connectingsaid evaluation circuit to said scattered radiation smoke detector; saidscattered radiation smoke detector comprising at least one first opticalcollimator for directing electromagnetic radiation into said measuringvolume in a predetermined direction; said at least one optical conductorpair comprising at least one optical transmission conductor forconducting said electromagnetic radiation from said means for emittingelectromagnetic radiation to said at least one first optical collimator;said scattered radiation smoke detector comprising at least one secondoptical collimator for receiving electromagnetic radiationforward-scattered from smoke within said measuring volume; said at leastone optical conductor pair comprising at least one optical receptionconductor for conducting said received forward-scattered electromagneticradiation back to said evaluation circuit; said evaluation circuitcomprising means for sensing and evaluating said electromagneticradiation conducted back for determining a possible presence of smoke insaid measuring volume; said at least one first optical collimatordefining a radiation zone extending in said predetermined direction andbeing substantially non-divergent; said at least one second opticalcollimator defining a forward-scattering reception zone extending at anangle of less than 90° to said predetermined direction and beingsubstantially non-divergent; and said forward-scattering reception zoneintersecting said radiation zone within said measuring volume.
 19. Thesmoke detection system as defined in claim 18, wherein:said angle ofless than 90° lies substantially between 5° and 15°.
 20. The smokedetection system as defined in claim 18, further including:shieldingmeans arranged to preclude inadvertent direct irradiation of said atleast one second optical collimator by said at least one first opticalcollimator.
 21. The smoke detection system as defined in claim 18,further including:at least one third optical collimator for receivingscattered electromagnetic radiation and defining a scattering receptionzone extending at an angle to said predetermined direction greater thansaid angle of less than 90°; and a further optical conductor forconducting said received scattered electromagnetic radiation back tosaid evaluation circuit.
 22. The smoke detection system as defined inclaim 21, wherein:said scattering reception zone defines abackward-scattering reception zone extending at an angle of more than90° to said predetermined direction.
 23. The smoke detection system asdefined in claim 18, wherein:said means for emitting saidelectromagnetic radiation is capable of emitting said electromagneticradiation at a plurality of different ranges of wavelength.
 24. Thesmoke detection system as defined in claim 18, further including:atleast one third optical collimator for receiving forward-scatteredelectromagnetic radiation and defining a radiation reception zoneextending at an angle of less than 5° to said predetermined directionand being substantially non-divergent; said radiation reception zoneintersecting said radiation zone within said measuring volume; and afurther optical conductor for conducting said received forward-scatteredelectromagnetic radiation back to said evaluation circuit.
 25. The smokedetection system as defined in claim 24, wherein:said angle of less than5° is substantially 0°.
 26. The smoke detection system as defined inclaim 18, wherein:said means for emitting said electromagnetic radiationis capable of emitting said electromagnetic radiation in pulses.
 27. Thesmoke detection system as defined in claim 18, wherein:said evaluationcircuit comprises a signal-processing circuit for comparing saidelectromagnetic radiation conducted back to said evaluation circuit withsaid electromagnetic radiation emitted by said means of said evaluationcircuit for emitting electromagnetic radiation.
 28. The smoke detectionsystem as defined in claim 27, wherein:said signal-processing circuitcomprises a phase-sensitive amplifier.
 29. The smoke detection system asdefined in claim 28, wherein:said phase-sensitive amplifier comprises alock-in amplifier.
 30. The smoke detection system as defined in claim18, further including:a radiation trap for terminating said radiationzone.
 31. The smoke detection system as defined in claim 18, furtherincluding:a radiation trap for terminating said forward-scatteringreception zone.
 32. A smoke detection system, comprising:a scatteredradiation smoke detector containing a measuring volume; an evaluationcircuit having means for emitting electromagnetic radiation and meansfor generating an alarm signal upon detecting a presence of smoke insaid measuring volume; at least one optical conductor pair connectingsaid evaluation circuit to said scattered radiation smoke detector; saidscattered radiation smoke detector comprising at least one first opticalcollimator for directing electromagnetic radiation into said measuringvolume in a predetermined direction; said at least one optical conductorpair comprising at least one optical transmission conductor forconducting said electromagnetic radiation from said means for emittingelectromagnetic radiation to said at least one first optical collimator;said scattered radiation smoke detector comprising at least one secondoptical collimator for receiving electromagnetic radiationforward-scattered from smoke within said measuring volume; said at leastone optical conductor pair comprising at least one optical receptionconductor for conducting said received forward-scattered electromagneticradiation back to said evaluation circuit; said evaluation circuitcomprising means for sensing and evaluating said electromagneticradiation conducted back for determining a possible presence of smoke insaid measuring volume; said at least one first optical collimatordefining a radiation zone having substantially the form of a conoidgenerated about an axis of revolution extending in said predetermineddirection and substantially confined to a small thickness; said at leastone second optical collimator defining a forward-scattering receptionzone having substantially the form of a conoid generated about an axisof revolution extending in said predetermined direction andsubstantially confined to a small thickness; and said forward-scatteringreception zone intersecting said radiation zone in a substantiallycircular ring of small diameter within said measuring volume.
 33. Ascattered radiation smoke detector, comprising:an electronic evaluationcircuit; a plurality of electromagnetic radiation conducting elementsfor connecting said electronic evaluation circuit to the smoke detector;said electronic evaluation circuit comprising means for emittingelectromagnetic radiation; a measuring volume; at least one firstelectromagnetic radiation conductor of said plurality of electromagneticradiation conductors serving for radiating said electromagneticradiation emitted by said means into said measuring volume; at least onesecond electromagnetic radiation conducting element of said plurality ofelectromagnetic radiation conducting elements serving for receiving andconducting back to said electronic evaluation circuit electromagneticradiation scattered by smoke particles in said measuring volume; said atleast one first electromagnetic radiation conducting element having anelectromagnetic radiation exit end; said at least one secondelectromagnetic radiation conducting element having an electromagneticradiation entry end; a respective optical arrangement at each of saidelectromagnetic radiation exit end and said electromagnetic radiationentry end; each said optical arrangement comprising a radiation emissioncollimating device and a radiation reception collimating device; eachsaid optical arrangement defining an at least approximatelynon-divergent radiation zone of small cross-section and an at leastapproximately non-divergent reception zone of small cross-section; andsaid at least approximately non-divergent radiation zone and said atleast approximately non-divergent reception zone of both said opticalarrangements mutually intersecting in said measuring volume forgenerating said at least approximately non-divergent radiation zone witha small cross-section and said at least approximately non-divergentreception zone with a small cross-section.
 34. The scattered radiationsmoke detector as defined in claim 33, wherein:said electromagneticradiation emitted by said means is pulsed.
 35. The scattered radiationsmoke detector as defined in claim 33, wherein:the scattered radiationsmoke detector is connectable to said electronic evaluation circuit; andsaid electronic evaluation circuit comprising a coincidence circuit forcomparing electromagnetic radiation received and electromagneticradiation emitted by said means.
 36. The scattered radiation smokedetector as defined in claim 35, wherein:said coincidence circuitcomprises a phase-sensitive amplifier.
 37. The scattered radiation smokedetector as defined in claim 36, wherein:said phase-sensitive amplifiercomprises a lock-in amplifier.
 38. The scattered radiation smokedetector as defined in claim 33, wherein:said at least approximatelynon-divergent radiation zone of small cross-section is closed by aradiation trap.
 39. The scattered radiation smoke detector as defined inclaim 33, wherein:said at least approximately non-divergent receptionzone of small cross-section is closed by a radiation trap.
 40. A smokedetection system, comprising:a scattered radiation smoke detectorcontaining a measuring volume; an evaluation circuit having means foremitting electromagnetic radiation and means for generating an alarmsignal upon detecting a presence of smoke in said measuring volume; atleast two optical conductor pairs connecting said evaluation circuit tosaid scattered radiation smoke detector; said scattered radiation smokedetector comprising at least two first optical collimators for directingelectromagnetic radiation into said measuring volume in a predetermineddirection; said at least two optical conductor pairs comprising at leasttwo optical transmission conductors for conducting said electromagneticradiation from said means for emitting electromagnetic radiation to eachof said at least two first optical collimators; said scattered radiationsmoke detector comprising at least two second optical collimators forreceiving electromagnetic radiation forward-scattered from smoke withinsaid measuring volume; said at least two optical conductor pairscomprising at least two optical reception conductors for conducting saidreceived forward-scattered electromagnetic radiation back to saidevaluation circuit; said evaluation circuit comprising means for sensingand evaluating said electromagnetic radiation conducted back by each ofsaid at least two optical reception conductors for determining apossible presence of smoke in said measuring volume; said at least twofirst optical collimators defining at least two radiation zones eachextending in said predetermined direction and being substantiallynon-divergent; said at least two second optical collimators defining atleast two forward-scattering reception zones each extending at an angleof less than 90° to said predetermined direction and being substantiallynon-divergent; and each forward-scattering reception zone of said atleast two forward-scattering reception zones intersecting an associatedone of said at least two radiation zones within said measuring volume.